This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Carbonate of potassium should be kept in well-stopped bottles. A white, crystalline or granular powder, very deliquescent, odorless, having a strongly alkaline taste, and an alkaline reaction. Soluble in 1 part of water at 15° C. (59° F.), and in 0.7 part of boiling water; insoluble in alcohol.
One part by weight in nine parts of distilled water (10 per cent.). Filter. Specific gravity 1.092 at 15° C. The commercial salt contains water in various proportions, sometimes in considerable quantities, without appearing damp. Its solution should therefore be regulated by the hydrometer, 100 parts containing 10 parts of dry salt. Proportion 10 to 1.